Lighting using point light sources such as LED lighting is rapidly gaining popularity because of its long lifetime and low power consumption. In addition, due to the configurability of LED lighting, such lighting is routinely integrated in lighting systems that deliver configurable lighting to an environment in which the lighting system is installed. Such lighting systems may include lighting systems in which a plurality of different light sources are interconnected using wireless or wired communication technologies.
An example of LED lighting for use in such lighting systems is LED lighting strips, in which the LEDs are typically distributed along a strip at regular distances from each other, which regular distance is commonly referred to as the pitch of the LEDs. As such LED lighting may be used in a wide variety of environments having different lighting requirements, different LED lighting strips may require LEDs at different pitches in order to deliver the required lighting requirements. Consequently, different LED lighting strips need to be manufactured for such different requirements, which is costly to the manufacturer of such LED lighting and lighting systems including such LED lighting.
Linear lighting elements such as lighting strips are used in multiple applications and are also increasingly finding their way into people's homes. Various manufacturers provide fixed length LED lighting strips in a rigid housing, which facilitates handling and mounting. They may also incorporate optical or light shaping elements (e.g. a diffuse exit window). The disadvantage of these products is that they have a fixed length and cannot be cut to size.
Other LED lighting strip products that are becoming commonplace are flexible LED strips. Their flexibility allows for compact packaging and easy shipping and allows the user to conform the LED lighting strip to the object it is to be applied to, for example by having a bendable strip. In practice however the strips are mostly used as linear elements. An additional advantage of flexible LED lighting strips is that they may, in many cases, be cut-to measure at discrete intervals, i.e. an excess part can be cut off. The cut-off part is cast away.
Example applications of such lighting products are cove lighting, underneath cupboards, behind stair handrails, under kitchen cupboards, etc. For most of these applications, the length required for the lighting strip to exactly fit the object or structural element to which the lighting strip will be applied is not available. Fitting the lighting strip to the exact length of the object or structure however greatly enhances the aesthetic characteristics.
For rigid LED lighting strips, this typically means the light effect does not extend to the edges of the object giving dark edges, or multiple LED lighting strips are used for longer objects with spaces in between. This results in darker areas at those locations. This is aesthetically not optimal and can often appear cheaper or the lighting can look like an afterthought.
Flexible cut-to-measure LED strips can be cut to the required length, but for many users cutting into the LED strip is not desired: Apart from the fact that it means cutting into an electrical device, it is also irreversible and the excess part cannot be reused. This irreversible cutting process, combined with the fact that the strips are usually fixed on the surface with an adhesive tape, prohibits a user to try out the lighting strip in different locations and orientations, before deciding on a final location. After installation, the strip is hard to remove and cannot be easily reused in another location. If it can be removed, it can no longer be used for longer lengths.
One way to avoid the cutting process is simply to overlap lighting strips to create a reduced overall length. However, this gives non-uniformity of the brightness, for example if both of the overlapping strips create light at the overlap area. For example, two 1 meter lighting strips may be used to fill a space of 1.5 m, by overlapping them over 0.5 m in the middle. This creates more light in the overlapping section and hence a non-homogeneous light effect), which also implies a higher and unnecessary energy consumption.
There is therefore a need for a linear lighting element which can be adjusted to length, but without requiring cutting to length, and which still provides a uniform light output.
U.S. patent application 2013/141914 A1 discloses a lamp including a first light device and a second light device. The first light device includes a first cover and a first light strip received in the first cover. The second light device included a second cover and a second light strip received in the second cover. The second light device is movably mounted to the first light device. A light emitting area of the second light strip of the second light device is changeable according to movement of the second light device relative to the first light device whereby a total light emitting area of the LED lamp is adjustable.